This application is based on Japanese Patent Application No. 2002-275681 filed on Sep. 20, 2002, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an ejector cycle (vapor-compression refrigerant cycle) having an ejector that is used as a decompression unit, and an arrangement structure of the ejector cycle in a vehicle.
2. Related Art
In a conventional ejector cycle described in JP-A-5-149652, low-pressure gas refrigerant in an evaporator is sucked into an ejector while high-pressure refrigerant is decompressed in a nozzle of the ejector, and pressure of refrigerant to be sucked into a compressor is increased in a pressure-increasing portion of the ejector. Therefore, liquid refrigerant in a gas-liquid separator is circulated to the evaporator by a pump operation of the ejector. In the ejector cycle, a throttle unit such as an orifice and a capillary tube is generally provided between the evaporator and the gas-liquid separator, for sufficiently reducing the pressure and the temperature of the refrigerant supplied to the evaporator. However, when a refrigerant passage length between the throttle and the evaporator is long, a part of refrigerant in the refrigerant passage may be evaporated by absorbing heat from outside before flowing into the evaporator. Thus, gas-liquid two-phase refrigerant is introduced into the evaporator, and a cooling capacity (heat-absorbing capacity) in the evaporator is decreased.
Furthermore, when the gas-liquid two-phase refrigerant is supplied into plural tubes extending vertically in an evaporator from an upper side thereof, high-density liquid refrigerant tends to flow into the plural tubes in the vicinity of its inlet, and gas refrigerant tends to flow into the plural tubes separated from the inlet. Thus, the surface temperature of the evaporator is different at different positions, and the temperature distribution of the evaporator is deteriorated.
In view of the above-described problems, it is an object of the present invention to provide an ejector cycle, which effectively improves a cooling capacity.
It is another object of the present invention to restrict a temperature distribution difference in an evaporator of the ejector cycle.
It is further another object of the present invention to provide a simple arrangement structure of the ejector cycle in a vehicle while improving the cooling capacity.
According to the present invention, an ejector cycle includes a compressor for compressing refrigerant, a high-pressure heat exchanger disposed outside of a compartment for radiating heat of high-pressure refrigerant discharged from the compressor, a low-pressure heat exchanger disposed in the compartment for evaporating low-pressure refrigerant after being decompressed, an ejector including a nozzle for decompressing and expanding high-pressure refrigerant flowing from the high-pressure heat exchanger, a gas-liquid separator for separating refrigerant discharged from the ejector into gas refrigerant and liquid refrigerant, and a throttle for decompressing refrigerant flowing from the gas-liquid separator into the low-pressure heat exchanger. The ejector sucks gas refrigerant evaporated in the low-pressure heat exchanger by using a refrigerant flow jetted from the nozzle, and increases a pressure of the refrigerant to be sucked to the compressor. In the ejector cycle, the throttle is provided in the compartment. Therefore, a length of a refrigerant passage from the throttle to the low-pressure heat exchanger can be made shorter. Thus, it can restrict a part of refrigerant from the throttle from being evaporated by absorbing heat from the atmosphere, before being introduced to the evaporator. As a result, cooling capacity of the low-pressure heat exchanger can be improved when the ejector cycle is used for an air conditioner. In addition, because it can restrict gas-liquid two-phase refrigerant from flowing into the low-pressure heat exchanger, a refrigerant distribution to be introduced to the low-pressure heat exchanger can be improved.
Further, when the ejector cycle is disposed in a vehicle, the low-pressure heat exchanger is disposed in a passenger compartment, and the gas-liquid separator and the ejector are disposed in an engine compartment. Even in this case, because the throttle is disposed in the passenger compartment adjacent to the evaporator, the refrigerant pipe length between the throttle and the low-pressure heat exchanger can be made shorter, so that cooling performance in the low-pressure heat exchanger can be improved.
Preferably, an additional heat exchanger is disposed to perform heat exchange between refrigerant flowing from the gas-liquid separator to the low-pressure heat exchanger and refrigerant to be sucked to the elector from the low-pressure heat exchanger. In this case, the throttle is disposed in a refrigerant passage through which liquid refrigerant is introduced from the gas-liquid separator to an inlet of the low-pressure heat exchanger, between an outlet of the additional heat exchanger and the inlet of the low-pressure heat exchanger. Therefore, the refrigerant to be introduced to the low-pressure heat exchanger can be cooled, and refrigerant approximately in one liquid phase state can be introduced to the low-pressure heat exchanger.
On the other hand, the low-pressure heat exchanger includes a plurality of tubes extending substantially vertically, an upper header tank connected to upper ends of the tubes to communicate with the tubes, and a lower header tank connected to lower ends of the tubes to communicate with the tubes. In this case, a refrigerant inlet is provided in the lower header tank. Therefore, refrigerant is introduced into the low-pressure heat exchanger upwardly through the refrigerant inlet. Accordingly, it can reduce a temperature difference in a surface of the low-pressure heat exchanger due to a density difference between gas refrigerant and liquid refrigerant.